Definition
Power is the rate at which work is done or energy is transferred or transformed over time. Mathematically, it is defined as:
- How to read: “Power P is equal to work W divided by time t.”
- Meaning / when to use: Use to calculate how fast energy is being consumed or generated. One Watt (W) of power is equal to 1 Joule of work done per second.
Why It Matters
Power determines the performance capacity and throughput of a system. A high-power machine can do work very quickly (e.g. accelerating a car in seconds or processing data at high speed), whereas a low-power machine takes longer to do the same amount of work. It is the defining metric for engine performance, electrical grids, microprocessors, and human athletic output.
Core Concepts
- Rate of Consumption: Power measures the speed of energy usage, not the total quantity. A 100-watt lightbulb uses energy 10 times faster than a 10-watt bulb.
- Force and Velocity: Power can also be expressed as the product of force and speed:
- How to read: “Power equals force times velocity.”
- Meaning: To maintain a high speed against resistance (like aerodynamic drag), an engine must produce high power.
- Electrical Power: Calculated as current times voltage (). In electrical systems, high voltage allows for low current to deliver the same power, minimizing resistive heat losses in transmission lines.